PB2441: CD34+ CELL DOSE EFFECTS ON CLINICAL OUTCOMES OF ALLO-HEMATOPOIETIC STEM CELL TRANSPLANTATION (ALLO-HSCT)
Authors: Shengnan Zhou, Min Xiong, Gen Wang
Journal: HemaSphere (2023)

Topic: 22. Stem cell transplantation - Clinical Background: Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is one of the most important treatment options for hematologic malignancies. The efficacy allo-HSCT is associated with multiple factors such as pretreatment regimen, donor selection, stem cell dose, and disease type,eg. Among them, the effect of stem cell number on HSCT is inconclusive. Aims: The aim of our present study is to understand the efficacy of CD34+ cell doses on HSCT outcomes of our hospital. Methods: We retrospectively analyzed the clinical characteristics of 321 patients with AML or B-ALL who underwent HSCT in our hospital from January 2014 to December 2021. 157 patients with acute myeloid leukemia. ALL others 164 patients with acute lymphoblastic leukemia. The male to female ratio was 1:3. The median age was 22.3 years (range:1-69 years). The median disease course from diagnosis to transplant was 18 months (range: 11-41months). The conditioning regimen was Bu/cy/ATG or TBI/Cy/ATG. Patients underwent a matched unrelated donor (MUD) HSCT, sibling allogeneic, or related haploidentical. For GVHD prophylaxis, we used CsA/tacrolimus +MMF+ sMTX for all of the patients. We stratified patients according to disease risk. 132 patients with acute leukemia in the first complete remission (CR) were defined as Low-risk diseases. ALL other 185 patients who had any other status were assigned to high-risk diseases. Patients with different disease risk were divided into two groups according to the infused CD34+ cell doses: the high-CD34 group (infused CD34+ cells ≥8 × 10^6/kg), and the low-CD34 group (<8×10^6/kg). Median follow-up was 24 months (range, 1-84 months). We compared the GVHD, relapse incidence (RI) and overall survival (OS) of the cohort. Results: In the patients with different groups, median time to neutrophil and platelets engraft-ment was 14 days VS 15 days and 12 days VS 13 days, no statistical difference. In the patients with low-risk diseases: the high-CD34+ cell dose group showed lower relapse incidence (4.2% vs. 9.3%, P = 0.014) than did the low-CD34+ cell dose group. without any increase in graft-versus-host disease (GVHD).Although incidence of grades I-II aGVHD and chronic GVHD were elevated (17.8% vs. 25% P=.01 and 31.8% vs. 41.7% p=.012), grade III/IV acute GVHD (17.8% vs 8.3%, P =.016) was decreased, and OS was trending upward(68.2% vs 87.5%, P =.0054). Meanwhile, a higher CD34+ cell dose had no impacts on the outcomes of the grades I-II aGVHD (12.7% vs.16.7% p=.527) grade III/IV acute GVHD (15.5% vs 12.5%, P =.24), cGVHD(31.7% vs 33.3%, P=.627), relapse incidence (23.9% vs. 14.6%, P = 0.129) and overall survival (OS)(64.8% vs 60.4%, P =.281) of patients with high-risk diseases. Summary/Conclusion: Our data showedthat: the high-dose CD34+ cell was associated with a lower relapse incidence and elevated OS trend. Hower, there was no good correlation in the-high group. In the future studies, the correct dose of CD34+ cell should be further discussed through multi-factor analysis and larger number of cases. Keywords: Allo-SCT, CD34+ cells, Allogeneic bone marrow transplant